Molecular ink-derived chalcogenide thin films: Solution-phase mechanisms and solar energy conversion applications

The use of solution processing to fabricate metal chalcogenide thin films has gained considerable interest because of its low cost and scalability compared to vacuum deposition. Among the various types of solution processing, homogeneous molecular ink-based processes can lead to high-quality metal chalcogenide thin films, a prerequisite for high-efficiency solar energy conversion devices. In this review, we summarise studies on the fundamental understanding of the solution-phase mechanism of various types of molecular inks classified into three categories: hydrazine-, thiol-amine-, and organochalcogen-complex-based systems. The unique chemistry of each system is presented in conjunction with appropriate characterisation techniques to understand molecular interactions. Additionally, we also survey the recent solar energy conversion applications, such as solar cells and photoelectrodes for water splitting, with chalcogenide thin-film light absorbers prepared using each molecular ink technique. The strengths, limitations, and future possibilities of each system are discussed to provide insight into future advancements in molecular ink-derived chalcogenide thin films.